1. Field of the Invention
The present invention relates to a method of fabricating a semiconductor device, and more particularly to a method of fabricating a semiconductor device which has a fuse box and uses an etch stop film, so that an insulating film left on the fuse box can have a constant thickness.
2. Description of the Prior Art
In general, the process yield of the semiconductor device can be improved upon fabricating extra lines to replace row and column lines to prevent the entire chip from failing when one cell from row and column lines in the semiconductor device fails. The process yield can also be improved by providing a plurality of fuse boxes having a plurality of fuses to replace inferior lines, and utilizing a repair method to be connected to a new line by cutting the fuse connected to the corresponding line.
On the other hand, in the case of forming a multiple layer in the semiconductor device, the thick insulating films are formed on the fuse boxes by the following process. In general, the fuse is to be connected, for example, by a bit line or a word line formed on the semiconductor substrate. It is necessary to maintain a constant thickness on the insulating film on the surface of the the fuse box, because a cutting process performs exactly at the fuses which connect with the failed lines after completing the repair process and testing of the chip of the semiconductor device.
In addition, the number of layers in a metal wiring layer increases due to the semiconductor device gradually becoming of higher integration. As a result, the thickness of the insulating film on the fuse box increases.
Furthermore, the thickness of the insulating film on the fuse box differs according to its location in the chip. The difference in thickness makes accurately cutting the fuse at the fuse box impossible during the repair process.
FIG. 1 shows a lay-out view of a general fuse box, where a plurality of fuses 2 are arranged in fuse box 4.
FIG. 2 is a sectional view showing a state of the fuse box, after completing the semiconductor device according to the prior art, which is shown according to line A--A of FIG. 1.
Provided is a conductive layer used as a fuse 11 on a lower insulating film 10. An upper insulating film 13 will become thicker by the next process, and the upper insulating film 13 formed on fuse box is removed to carry out the repairing process until the upper insulating film 13 on the fuse 11 remains a constant thickness B. In addition, if the fuse 11 is exposed to the atmosphere, it will corrode; thus, the surface of the fuse must have a constant thickness for the insulating film.
Therefore, there are no problems if the insulating film on the fuse remains even in the whole chip, but there is a problem when the process yield of fabricating the semiconductor device decreases, which is brought about by the interior repairing process where the fuse is not completely cut. Since the difference in thickness is dependant upon the location of chip, the remaining insulating film is not removed completely.